Multiplication function

multProc.pep

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      Object
Addr  code   Symbol   Mnemon  Operand     Comment
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0000  04002B          BR      main        

             mainFram:.EQUATE 6           ;Size of main's local variables
             en:      .EQUATE 0           ;main local variable #2d
             em:      .EQUATE 2           ;main local variable #2d
             prod:    .EQUATE 4           ;main local vairbale #2d
0003  0A506C prompt:  .ASCII  "\nPlease enter two numbers to multiply: \x00"
      656173 
      652065 
      6E7465 
      722074 
      776F20 
      6E756D 
      626572 
      732074 
      6F206D 
      756C74 
      69706C 
      793A20 
      00     

002B  24     main:    NOP0                
002C  680006          SUBSP   mainFram,i  ;allocate #prod #em #en
002F  410003          STRO    prompt,d    
0032  330002          DECI    em,s        ;input original m
0035  330000          DECI    en,s        ;input original n

             ;Prepare argument N for mult
0038  C30000          LDA     en,s        
003B  E3FFFA          STA     argN,s      

             ;Prepare argument M for mult
003E  C30002          LDA     em,s        
0041  E3FFFC          STA     argM,s      

             ;Call mult
0044  680006          SUBSP   frame,i     ;allocate #return #paramM #paramN
0047  160066          CALL    mult        
004A  600006          ADDSP   frame,i     ;deallocate #paramN #paramM #return

             ;Save returned value
004D  C3FFFE          LDA     retval,s    
0050  E30004          STA     prod,s      

             ;Display result
0053  3B0002          DECO    em,s        
0056  50002A          CHARO   '*',i       
0059  3B0000          DECO    en,s        
005C  50003D          CHARO   '=',i       
005F  3B0004          DECO    prod,s      

0062  600006          ADDSP   mainFram,i  ;deallocate #en #em #prod
0065  00              STOP                



             ;procedure mult
             ;callER data
             frame:   .EQUATE 6           ;size of mult's arguments and return
             argN:    .EQUATE -6          ;mult argument
             argM:    .EQUATE -4          ;mult argument
             retval:  .EQUATE -2          ;mult return

             ;callEE data
             lframe:  .EQUATE 6           ;size of mult's local variables
             dec:     .EQUATE 0           ;mult local variable #2d
             inc:     .EQUATE 2           ;mult local variable #2d
             product: .EQUATE 4           ;mult local variable #2d

             retAddr: .EQUATE 6           ;mult return address #2h

             paramN:  .EQUATE 8           ;mult formal parameter #2d
             paramM:  .EQUATE 10          ;mult formal parameter #2d
             return:  .EQUATE 12          ;mult return value #2d

             ;Entry point for mult
0066  24     mult:    NOP0                
0067  680006          SUBSP   lframe,i    ;allocate #product #inc #dec

             ;product=0
006A  C00000          LDA     0,i         
006D  E30004          STA     product,s   

             ;inc = n
0070  C30008          LDA     paramN,s    
0073  E30002          STA     inc,s       
             ;dec = m
0076  C3000A          LDA     paramM,s    
0079  E30000          STA     dec,s       

007C  24     loop:    NOP0                
007D  C30000          LDA     dec,s       
0080  0A00AD          BREQ    done        ;Nothing more to multiply
0083  22              RORA                ;Put parity of dec into C
0084  14008E          BRC     odd         ;if dec%2==1
0087  04008A          BR      even        ;if dec%2==0

             ;In case of a 0, nothing to do
008A  24     even:    NOP0                
008B  04009B          BR      always      

             ;In case of a 1, the product goes up by inc
008E  24     odd:     NOP0                

             ;product = product + inc
008F  C30004          LDA     product,s   
0092  730002          ADDA    inc,s       
0095  E30004          STA     product,s   
0098  04009B          BR      always      

009B  24     always:  NOP0                
             ;dec = dec/2
009C  C30000          LDA     dec,s       
009F  1E              ASRA                
00A0  E30000          STA     dec,s       
             ;inc = 2*inc
00A3  C30002          LDA     inc,s       
00A6  1C              ASLA                
00A7  E30002          STA     inc,s       

00AA  04007C          BR      loop        

00AD  24     done:    NOP0                

             ;return product
00AE  C30004          LDA     product,s   
00B1  E3000C          STA     return,s    
00B4  600006          ADDSP   lframe,i    ;deallocate #dec #inc #product
00B7  58              RET0                


00B8                  .END                  
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Symbol table
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Symbol    Value        Symbol    Value
--------------------------------------
always    009B         argM      FFFC
argN      FFFA         dec       0000
done      00AD         em        0002
en        0000         even      008A
frame     0006         inc       0002
lframe    0006         loop      007C
main      002B         mainFram  0006
mult      0066         odd       008E
paramM    000A         paramN    0008
prod      0004         product   0004
prompt    0003         retAddr   0006
return    000C         retval    FFFE
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